Test system supporting reverse compliance

Abstract

An exemplary test system includes a power amplifier circuit that applies voltage or current to a test channel and one or more processing units configured to control the power amplifier circuit to follow a compliance curve. The compliance curve relates the output of the voltage to the output of the current. According to the compliance curve, the maximum current output increases as the absolute value of the output of the voltage increases.

Description

Technology Field

[0001] This specification describes an example of an implementation of a test system that supports a compliance curve in which the current of a test channel increases as the voltage of the test channel increases. Background Technology

[0002] The test system is configured to test the operation of electronic devices, such as microprocessors and memory chips. The test may include steps of sending a signal to the device and determining how the device responded to such a signal based on the response. For example, the test may include steps of applying voltage and current to a test channel and receiving a signal from the device based on the applied voltage and current. Depending on the device's response, it is determined whether the device passes or fails the test. The problem to be solved

[0003] According to the present invention, a test system that supports a compliance curve in which the current of a test channel increases as the voltage of the test channel increases can be provided. means of solving the problem

[0004] An exemplary test system comprises a power amplifier circuit that applies voltage or current to a test channel and one or more processing units configured to control the power amplifier circuit to follow a compliance curve. The compliance curve relates the output of the voltage to the output of the current. According to the compliance curve, the maximum current output increases as the absolute value of the voltage output increases. The exemplary test system may include one or more of the following functions alone or in combination.

[0005] The above voltage may be a direct current (DC) voltage, and the above current may be a DC current. The exemplary test system may include a compensation loop. The compensation loop may include a voltage sensor that detects the voltage of the test channel, a current sensor that detects the current of the test channel, and one or more processing units that control the power amplifier circuit based on the voltage detected in the test channel and the current detected in the test channel. The exemplary test system may include a current clamp that limits the current of the test channel when the current detected in the test channel exceeds a predefined maximum value.

[0006] The compliance curve may be based on the magnitude of power that the test channel can dissipate. The compliance curve is a first compliance curve, and memory stores information for generating the second compliance curve or a second compliance curve related to the output of the voltage relative to the output of the current. According to the second compliance curve, the maximum current output decreases as the absolute value of the voltage output increases. The one or more processing units are configured to control the power amplifier circuit based on either the first compliance curve or the second compliance curve. At least one of the first compliance curve or the second compliance curve includes a step function. The first compliance curve may include a step function, and the second compliance curve may include a step function.

[0007] The one or more processing units may be configured to implement a controller including a proportional-integral-derivative controller to control the power amplifier circuit. The exemplary test system may include a display device that displays a function based on the compliance curve to a user and an input device that programs a voltage based on the function. The function may be the compliance curve. The function may be a step function that falls within the boundary of the compliance curve.

[0008] Controlling the power amplifier circuit to follow the compliance curve may include setting the current. The current setting may be based on the magnitude of power that the test channel can consume, the maximum voltage, and the voltage programmed into the test system. The current setting may be adjusted so that the voltage programmed into the test system is less than or equal to the difference between the maximum voltage and the overhead voltage.

[0009] The power amplifier circuit may include an output stage for the test channel connected to a reference voltage and a return conductor. The reference voltage may be higher than the voltage of the return conductor. The voltage of the return conductor may not be zero. The compliance curve may be a first compliance curve, and controlling the power amplifier circuit to follow the first compliance curve may include setting the current based on the voltage programmed into the test system. The first compliance curve may enable a test channel density greater than that enabled by a second compliance curve, in which the maximum current output decreases as the voltage output increases. The power amplifier circuit may include an output stage. The output stage may have a physical size corresponding to the power consumption of the output stage. Using the second compliance curve above can cause a power output for the device under test (DUT) that is greater than the power output caused by using the first compliance curve, so that a reduction in the physical size of the output stage is possible by using the first compliance.

[0010] The power amplifier circuit may include an output stage for the test channel connected to a first reference voltage and a second reference voltage. The first reference voltage may be higher than the second reference voltage. The exemplary test system may include a voltage sensor for detecting the voltage on the test channel. The one or more processing units may be configured to control at least one of the first reference voltage or the second reference voltage based on the voltage on the test channel to control the power output for the test channel. At least one of the first reference voltage or the second reference voltage is programmable.

[0011] The exemplary test system described above may include a memory that stores a function for generating the compliance curve or the second compliance curve. The first compliance curve may include a curve in which the current increases as the voltage increases up to a certain point. After that point, the current may remain constant over the increasing voltage range. The voltage may be an alternating current (AC) voltage and the current may be an AC current.

[0012] An exemplary method comprises the steps of: receiving a voltage as an input to a test system; selecting a compliance curve based on the voltage, wherein the maximum current output increases as the absolute value of the voltage output increases according to the compliance curve; generating a current output based on the voltage input and the compliance curve; and outputting the voltage and current to a test channel of the test system.

[0013] An exemplary test system comprises: an output stage having a power amplifier circuit that applies voltage or current to a test channel that is part of a connection to a DUT; a current clamp that limits the current of said test channel; and one or more processing units configured to dynamically control said current clamp based on the voltage across said DUT. The exemplary test system may include one or more of the following functions alone or in combination.

[0014] Power consumption through the output stage is based on the product of the current through the DUT and the difference between the voltage of the output stage and the voltage of the DUT. Dynamically controlling the current may include controlling the current limit of the test channel. Controlling the current clamp may include programming the current clamp. The one or more processing units may be configured to control the power amplifier circuit to follow a compliance curve. The compliance curve may correlate the output of the voltage with the output of the current. According to the compliance curve, the maximum current output increases as the absolute value of the voltage output increases.

[0015] Two or more features described in this specification, including this summary section, may be combined to form an implementation not specifically described in this specification.

[0016] At least part of the test system and process described herein may be configured or controlled by executing instructions stored in one or more non-transient machine-readable storage media on one or more processing units. Examples of non-transient machine-readable storage media include read-only memory, optical disc drives, memory disc drives, and random access memory. At least part of the test system and process described herein may be configured or controlled using a computing system composed of one or more processing units and memory storing instructions executable by the one or more processing units to perform various control operations.

[0017] Details of one or more implementations are described in the attached drawings and the following description. Other features and benefits will be apparent from the description, drawings, and claims. Brief explanation of the drawing

[0018] Figure 1 is a block diagram of an exemplary test system. Figure 2 is a graph showing exemplary existing compliance curves in both the proposed version and the actual version. Figure 3 is a graph showing a presented version of an exemplary existing compliance curve. Figure 4 is a graph showing the conventional compliance curve and the inverse compliance curve for the same output stage of the same test channel. Figure 5 is a graph showing exemplary inverse compliance curves in both the presented version and the actual version. Figure 6 is a graph showing exemplary inverse compliance curves in both the proposed version and the actual version. Figure 7 is a graph showing an exemplary reverse compliance curve including a current plateau. FIG. 8 is a block diagram showing exemplary components of an exemplary output stage of a test channel. FIG. 9 is a flowchart illustrating an exemplary process for generating voltage and current using one or more compliance curves. Similar reference numbers in different drawings represent similar elements. Specific details for implementing the invention

[0019] In some examples, the compliance curve specifies the power consumption of the test channel at the DUT (Device Under Test). In some cases, the test channel includes a physical medium through which signals are transmitted from the test system to the DUT and received at the DUT. In such cases, the test channel is part of the electrical and / or optical connection between the test system and the DUT.

[0020] Each exemplary test channel has an output stage that consumes a fixed amount of power for the input voltage. In some implementations, the input voltage may be programmable, in which case the power consumption of the output stage will change based on changes in voltage. Each test channel can be controlled by a compliance curve that specifies the current that can pass through the test channel for a given voltage. For example, the user can specify the voltage to be provided to the test channel. For that voltage, the compliance curve specifies, for example, one or more values ​​of the current range that the test channel can support. In some conventional compliance curves, as the voltage increases, the current also decreases. In inverse compliance curves, as the absolute value of the voltage increases, the current also increases. An example implementation of a test system that supports both inverse compliance curves and conventional compliance curves is described here. An example of the components of the test system is shown in Figure 1, which is described below.

[0021] In some implementations, each test channel of the test system includes an output stage comprising a power amplifier circuit (also referred to herein as "power amplifier") for applying voltage and current to the test channel. One or more processing units are configured to control the power amplifier circuit based on a compliance curve to provide power to the DUT. As described, the compliance curve relates the voltage output of the test channel to the current output (e.g., voltage and current delivered to the DUT). In the example, the compliance curve is an inverse compliance curve in which the maximum current output increases as the absolute value of the voltage output increases. However, the test system may also support a conventional compliance curve in which the maximum current output decreases as the voltage output increases. Multiple test channels (e.g., each test channel) may include an instance of the power amplifier circuit, one or more processing units dedicated to that test channel, or both an instance of the power amplifier circuit and one or more dedicated processing units.

[0022] A compliance curve can define the power consumption of a test channel in one or more quadrants of an operation graph. For example, a compliance curve can define the power consumption of a test channel in up to four quadrants of the graph, namely, positive voltage and positive current, positive voltage and negative current, negative voltage and positive current, or negative voltage and negative current. Thus, while the examples presented herein are generally limited to one or two quadrants, the features described in this specification may be used with a compliance curve that defines the power consumption of a test channel in any number of quadrants.

[0023] FIG. 2 illustrates an example of a conventional compliance curve (25) that defines the power consumption of a test channel (e.g., power consumption at the DUT) as a first quadrant (26), i.e., positive voltage (+V) and positive current (+I). As illustrated in FIG. 2, in this example, the magnitude of the current decreases as the magnitude of the voltage increases in the first quadrant (26). Each test channel output stage consumes a constant magnitude of power. Power to the DUT can be output by applying any appropriate current and voltage range to the test channel within the power consumption of the output stage. In some examples, power consumed by the test channel beyond what is defined by the compliance curve due to, for example, a short circuit of the voltage rail to ground, may cause the test channel to malfunction, become physically damaged, or both.

[0024] In some cases, the compliance curve includes only the operating range of the test channel provided to the user, rather than the entire operating range of the test channel. The user may select voltage and current from the presented compliance curve to ensure a safe and accurate operating range of the test channel. However, the actual compliance curve of the test channel extends beyond the compliance curve presented to the user. For example, in FIG. 2, the presented compliance curve (25) is a step function within the boundaries of the actual compliance curve (28). The actual compliance curve (28) is non-linear as illustrated in the figure and includes the entire presented compliance curve (25) and extends beyond it. The presented compliance curve does not track the boundaries of the actual compliance curve (28), thus reducing the risk of test channel power consumption at power levels beyond what the test channel can support. In this specification, the term "compliance curve" may mean the actual compliance curve, such as 28, or the presented compliance curve, such as 25.

[0025] Unlike the power consumption of the output stage, the instantaneous power delivered to the DUT is defined as the product of voltage and current at points within the compliance curve. In FIG. 2, this power is defined as the product of voltage and current selected within the compliance curve. In the exemplary compliance curve (25), this power for the DUT is generally nearly the same at points (22, 23, and 24). That is, as the voltage increases, the current decreases, but the product of the two remains the same. For example, FIG. 8 shows the components of an exemplary output stage. In FIG. 8, which will be described in more detail below, the power consumption of the output stage is equal to or proportional to the following voltage and current shown in the figure.

[0026] Power consumption ~((V+) -(Vd))*(ld),

[0027] Here, Vd is the voltage across the DUT, Id is the current drawn from the DUT, and V+ is the voltage output of the voltage regulator. In FIG. 8, the instantaneous power for the DUT is equal to or proportional to the following voltage and current shown in the figure.

[0028] Power to DUT ~(Vd)*(ld).

[0029] In some examples, the existing and inverse compliance curves are related to Vd and Id.

[0030] FIG. 3 illustrates another example of a conventional compliance curve (29) that defines the power consumption of a test channel in two quadrants with positive voltage (+V), positive current (+I) and negative voltage (-V), positive current (+I). As illustrated in the figure, in this example, the magnitude of the current decreases as the magnitude of the voltage increases in the first quadrant (30). In this example, in the second quadrant (31), the current remains constant and does not increase as the voltage increases.

[0031] As mentioned, in the inverse compliance curve, the current increases as the absolute value of the voltage increases. However, for a fixed-size test channel output stage, power consumption remains the same for all or part of the conventional and inverse compliance curves. For example, FIG. 4 shows examples of an inverse compliance curve (32) and a conventional compliance curve (33) for the same fixed-size output stage of a test channel. In the conventional compliance curve (33), 10 watts (W) of power consumption occurs for the segment envelope (36). In this example, (10V)*(1A) is equal to 10W. In the inverse compliance curve (32) supported by the same test channel, the same 10W of power consumption occurs for the segment envelope (37). In this example, (50V-40V)*(1A) is equal to 10W. Thus, power consumption is the same in different parts of the conventional and inverse compliance curves. At point (27) of the conventional compliance curve, the instantaneous power delivered to the DUT is 10W. That is, (10V) * (1A) equals 10W. In contrast, at point (34) of the inverse compliance curve, the instantaneous power delivered to the DUT is 50W. That is, (50V) * (1A) equals 50W. Therefore, by using inverse compliance, a larger amount of power can be provided using the same output stage of the test channel. In other words, a larger amount of power can be provided without increasing the size of the output stage. However, the test channel can support operation using both the conventional compliance curve and the inverse compliance curve.

[0032] In some cases, the inverse compliance curve includes only the operating range of the test channel provided to the user, rather than the entire operating range of the test channel. The user can select voltage and current from the presented inverse compliance curve to ensure safe and accurate operation of the test channel. However, the actual inverse compliance curve of the test channel extends beyond the presented inverse compliance curve presented to the user. For example, in FIG. 5, the presented inverse compliance curve (38) is a step function within the range of the actual compliance curve (39). The actual inverse compliance curve (39) includes the entire presented inverse compliance curve (38) as illustrated in the figure and extends beyond it. The presented inverse compliance curve (38) does not track the boundaries of the actual inverse compliance curve (39), and thus reduces the risk of test channel operation at power levels beyond what is supported by the test channel. In this specification, the term “inverse compliance curve” may refer to an actual inverse compliance curve such as 39 or an inverse compliance curve presented as 38.

[0033] FIG. 6 shows another example of two inverse compliance curves (40 and 41) defining the operating range of two test channels in two quadrants for positive voltage (+V), positive current (+I) (43) and positive voltage (+V), negative current (-I) (44). In this example, in the fourth quadrant (44), as the absolute value of the voltage increases (+V), the current (-I) increases to a maximum value. After that value, the current quickly becomes zero. In the fourth quadrant (44), a smaller negative current constitutes an increase in current. For example, -500 milliamperes (mA) is a current increase of more than -2 amperes (A). FIG. 6 also shows a compliance curve (46) presented as a dashed line for the actual compliance curve (40) and a compliance curve (47) presented as a dashed line for the actual compliance curve (41).

[0034] FIG. 7 shows another example of an inverse compliance curve (48) defining the operating range of a test channel in the first quadrant (49). In this example, the current increases non-linearly as the voltage increases to point (51). Alternatively, the current remains stable or constant over the increasing voltage range and then rapidly drops to zero. The area between the plateau (51) and the peak (53) is the overhead voltage (V 0H It corresponds to ). In the example, the overhead voltage required to support the current level of the ballast is the difference between the point where the compliance curve drops to 0 amperes (A) (to the right of the ballast, in volts) and the right side of the ballast (in volts). As the current increases, the required overhead voltage also increases, creating a peak in the compliance curve. In the example, the overhead voltage is supported by the voltage rails of the test system but includes a voltage that is some fixed voltage higher than the voltage that the user can select for the operation of the test channel. In some examples, the overhead voltage is 5 volts (V), 10 V, 15 V, 20 V, etc. The overhead voltage can be programmed into the test system and may be changed in some systems. A compliance curve such as that shown in Fig. 7 may be displayed to the user, but it shows the ballast without the peak.

[0035] Referring again to FIG. 1, the drawing illustrates components of an exemplary automated test equipment (ATE) (10) capable of supporting both conventional compliance curves and inverse compliance curves of the type described herein. However, in particular, conventional compliance curves and inverse compliance curves are not limited to use with the ATE of FIG. 1 or with the DUT described herein, but may be used in the appropriate technical context. In FIG. 1, dashed lines indicate potential signal paths between devices.

[0036] The ATE (10) includes a test head (11) and a test computer (12). The test head (11) interfaces with a DUT (not shown) on which a test is performed. The test computer (12) communicates with the test head (11) to control the test. For example, the test computer can download a set of test programs to the test device of the test head and then execute the set of test programs to test the DUT communicating with the test head. The computer (12) can also provide the user, for example, graphically with existing compliance curves and inverse compliance curves to show the user the capabilities of the test channel in the ATE (10).

[0037] The ATE (10) includes test devices (13A–13N). In this example, one or more of the test devices are VI (voltage-current) test devices configured to apply a direct current (DC) voltage and a DC current to a test channel and to receive a signal from a device based on the applied DC voltage and the applied DC current. However, other types of test devices may be used instead of or in addition to VI test devices. For example, a test device configured to generate an alternating current (AC) voltage and / or AC current signal having a frequency greater than 1 kilohertz (KHZ) may be used. Each test device may be configured to output a test signal to test the DUT and to receive a signal from the DUT. The received signal may include a response signal based on the test signal and / or a signal originating from the DUT that is not prompted by the test signal (e.g., does not respond).

[0038] A signal is transmitted to and received from the DUT through multiple test channels. In some examples, the test channel may include a physical transmission medium or media through which the signal is transmitted from the test device to the DUT and received from the DUT. The physical transmission medium may include, but is not limited to, an electrical conductor alone or an optical conductor, a wireless transmission medium, or an electrical conductor combined with both an optical conductor and a wireless transmission medium. In some examples, the test channel may include a frequency range through which the signal is transmitted via one or more physical transmission media.

[0039] In some implementations, different test channels of the ATE (10) may all support the same compliance curve, or different test channels of the ATE (10) may support different compliance curves. For example, output stages of different test channels may consume different amounts of power, or output stages of different test channels may consume the same amount of power. In some implementations, some test channels may support only the existing compliance curve, some test channels may support only the inverse compliance curve, some test channels may support both the existing compliance curve and the inverse compliance curve, and all test channels may support both the existing compliance curve and the inverse compliance curve.

[0040] The ATE (10) includes a connection interface (14) that connects a test device test channel (15) to a DIB (16). The connection interface (14) may include a connector (20) or other device for routing signals between the test device and the DIB (16). For example, the connection interface may include one or more circuit boards or other boards on which such connectors are mounted. Conductors defining the device test channel may be routed through the connection interface and the DIB.

[0041] In the example of FIG. 1, the DIB (16) is electrically and mechanically connected to the test head (11). The DIB includes a site (21) that may include pins, conductive traces, or other points of electrical and mechanical connection to which the DUT can connect. Test signals, response signals, and other signals pass over the site between the DUT and the test device through a test channel. The DIB (16) also includes, among other things, a connector, a conductive trace, and circuitry for signal routing between the test device, the DUT connected to the site (21), and other circuitry.

[0042] FIG. 8 illustrates an example of a component that may be included in the output stage of an exemplary test channel (60), such as the test channel of a test device (13A). As illustrated in FIG. 8, the output stage of the test channel (60) includes a power amplifier circuit (61). The power amplifier circuit may include a power amplifier configured to apply voltage and current to the transmission medium portion (64) of the test channel. The test channel also includes one or more processing units (55) configured to control the power amplifier circuit to follow one or more compliance curves. For example, the processing unit may implement a controller, such as a proportional-integral-derivative (PID) controller, to control the power amplifier circuit. In some implementations, the controller may include a feed-forward component in addition to the PID controller. In some examples, the compliance curve may be a conventional compliance curve, such as that illustrated in FIG. 2, 3, and 4, or an inverse compliance curve, such as that illustrated in FIG. 4 through 7. Computer memory that may be inside or outside the processing unit (65) can store the compliance curve.

[0043] The compliance curve may be retrieved from memory by the test computer (12) (of FIG. 1) to be displayed to the user on a display screen that is part of the test computer. In some implementations, the memory may define the compliance curve and store information or functions from which the compliance curve can be determined. In some implementations, the user can then select the voltage and / or current to be output to the test channel (e.g., DUT) within the operating range of the test device from the compliance curve. In some implementations, the user can select or program the voltage supported by the compliance curve, and the system can automatically determine the current based on that voltage. And, in some implementations, the user can select the current, and the system can automatically determine the voltage. The processing unit can then control the power amplifier, the voltage regulator (67), or both to apply the voltage and current to the test channel. Examples of the types of processing units that may be used are described herein.

[0044] As explained above, the power consumption of the output stage in FIG. 8 is equal to or proportional to the voltage and current shown in the drawing below.

[0045] Power consumption ~((V+) -(Vd))*(ld),

[0046] Here, Vd is the voltage across the DUT, Id is the current drawn from the DUT, and V+ is the voltage output of the voltage regulator. In some implementations, V+ can be changed via programming, which changes the power consumption of the output stage. Also, as explained earlier, the instantaneous power for the DUT in FIG. 8 is equal to or proportional to the following voltages and currents shown in the figure.

[0047] Power to DUT ~(Vd)*(ld).

[0048] In some examples, controlling the power amplifier circuit to apply voltage and current to the test channel and consequently the DUT according to an inverse compliance curve and / or an existing compliance curve includes a processing unit that determines the current. For example, the processing unit may determine the maximum current based on the magnitude of power the channel can support, namely the test channel consumption, the maximum voltage, and the voltage programmed into the test system by the user. For example, the processing unit may determine the maximum voltage based on the magnitude of power the channel can support, namely the test channel consumption, the maximum voltage, and the current programmed into the test system by the user.

[0049] In some examples, the user voltage (V prog ) or current (I ?One of the two is programmed, or neither is programmed. These are generally referred to as "force voltage" and "force current" modes, respectively. The electrical load of the DUT determines the variables that are not explicitly forced. This becomes clear when considering the case where the DUT is a simple resistor. It can be understood that the system can apply voltage to the resistor (having resistance R) and obtain a current defined as V / R (where V is the voltage across the resistor), or the system can apply current and obtain a voltage defined as l*R (where I is the current passing through the resistor). In some examples, voltage and current cannot be applied simultaneously. Therefore, the system applies either voltage or current, and the unforced variable is determined by the load provided to the channel. Another consideration here is that the unforced variable may have a user-programmable "clamp" that prevents the variable from exceeding a programmed value. For example, the value of the variable to be clamped can be set by programming. For instance, the current clamp value can be set dynamically according to the following relationship. In the example, the current clamp value can be dynamically set based on the voltage across the DUT, i.e., Vd, to limit the current of the test channel.

[0050] Power consumption ~((V+) -(Vd))*(ld)

[0051] By dynamically controlling the current clamp based on the voltage across the DUT, i.e., Vd, an initial curvature of the inverse compliance curve is generated. For example, in the example of Fig. 4, curvature occurs prior to 40V. In a system using only the existing compliance curve, when the current clamp is used, the maximum current of the test channel is preset and is not related to or dependent on Vd.

[0052] When the load causes the non-forced variable to exceed the clamped value, the VI channel dynamically changes its state (via the processing unit) to enforce the "non-forced" variable instead, ensuring that the clamp is not exceeded. Therefore, in summary, the exemplary channel can apply either voltage or current, but cannot apply both simultaneously. In this example, the channel can be configured as a dynamic switch that enforces between the two depending on the load, but still always enforces only one at a time, with the other determined by the load.

[0053] In the formula below regarding the power, voltage, and current of the test channel, "P" is the maximum power consumption of the test channel (known amount) and V HS Alternatively, V-high-side is the maximum voltage at which the test system can provide a selected compliance curve through the voltage rail.

[0054] In the formula below, when voltage is applied, I ? All variables except for can be known, and P is (V HS -V prog ) and (I ? It is the product of ). In the following formula, when current is applied, V prog All variables except for can be known, and P is (V HS -V prog ) and (I ? It is the product of ).

[0055] P=(V HS -V prog ) x (I ? )

[0056] The accurate setting of the current is the test system (V prog The voltage programmed into ) is the maximum voltage (V HS ) and overhead voltage (V 0H It can be adjusted to be less than or equal to the difference between ). That is,

[0057] V prog ≤ V HS -V OH

[0058] V prog Ga V HS -V 0H If it is larger, the test channel is operating near the maximum voltage provided by the voltage rail and may be susceptible to overvoltage conditions or other problems associated with operating at overvoltage.

[0059] The processing unit may be part of a compensation loop comprising a voltage regulator, a power amplifier circuit, a voltage sensor, and a current sensor. For example, the voltage regulator may be a programmable regulator that outputs a voltage range to the power amplifier (61). The power amplifier is configured to be controlled by the processing unit (65) to output the current and voltage derived from the voltage provided by the voltage regulator to the transmission medium portion (64) of the test channel. The voltage sensor (70) detects the voltage of the transmission medium portion (64) of the test channel and provides the level of the detected voltage to the processing unit (65). The current sensor (71) detects the current through a register (72) (in this example) on the transmission medium portion (64) of the test channel and provides the level of the detected current to the processing unit (65). An analog-to-digital converter (not shown) or a digitizer generates digital values ​​for the detected voltage and the detected current. The processing unit determines the magnitude of the power supplied from the test channel based on the digital values ​​of the detected voltage and the detected current, for example, by determining the product of the detected voltage and the detected current. In some implementations, an analog compensator may be used instead of a digital compensator. An analog compensator performs processing in the analog domain instead of the digital domain.

[0060] If the magnitude of power consumption in the transmission medium portion (64) of the test channel and accordingly through the DUT exceeds the power level of the compliance curve for the test channel, e.g., the existing compliance curve, the inverse compliance curve, or both the existing compliance curve and the inverse compliance curve, the processing unit controls the current clamp (74) to limit the magnitude of the current and the corresponding power in the test channel. The current clamp may be a high-speed dynamic clamp that cuts off or reduces the current when too much power is supplied. For example, the clamp may operate in the order of tens of microseconds (µs). The clamp limits current consumption when DIB / DUT load transients cause large voltage changes, thereby causing the supplied voltage and current to become overpowered in the compliance curve. This current clamp can be configured to reduce output stage power consumption to a sustainable limit, for example within 50 µs, and release in a time frame of several milliseconds (ms) to allow a user-defined voltage to take over from the compliance curve. The clamp may be implemented as part of a processing unit in a power amplifier, or the clamp may be hardware controllable by the processing unit or include such hardware. In this example, the clamp may be dynamically controlled by one or more processing units based on the voltage (Vd) across the DUT described earlier.

[0061] In some implementations, the output stage containing the power amplifier circuit is connected to a reference voltage (76) (V+) and a return conductor (75) (V-). The reference voltage is higher than the voltage of the return conductor and may be a voltage used to generate the current and voltage output from the transmission medium portion (64) of the test channel. For example, the reference voltage may be 5V, 10V, 50V, 100V, 300V, etc. In some examples, the voltage of the return conductor is set to a non-zero voltage. For example, the voltage of the return conductor is not at a ground level. For example, the voltage of the return conductor may be set to 1V, 2V, 3V, 5V, 10V, etc. The reason the return conductor of the output stage is 0V ("ground") or higher is to reduce the voltage-current (V*I) product in the output stage.

[0062] As described, in some implementations, controlling the power amplifier circuit to follow a compliance curve may involve setting the current output based on the voltage programmed into the test system. Using a reverse compliance curve can enable a channel density greater than that enabled by a conventional compliance curve (where current output decreases as voltage output increases). In this regard, the output stage, including the power amplifier circuit, has a physical size corresponding to the power consumption. By using a reverse compliance curve, the physical size of the output stage can be reduced compared to the physical size required when using a conventional compliance curve. More specifically, as described in relation to Fig. 4, using reverse compliance, the output stage of the test channel can provide 50V to the DUT. Using a conventional compliance curve for a fixed-size output stage provides only 10W to the DUT. Therefore, to generate a power output for the DUT using a conventional compliance curve that is similar to the power output generated using a reverse compliance curve, the size of the output stage must be increased. Therefore, using reverse compliance allows you to output greater instantaneous power to the DUT using a smaller output stage.

[0063] For example, to achieve a current output (12A) in a single test channel, the power consumption of the output stage is determined as follows using the existing compliance (30) of FIG. 3:

[0064] P=(96V-(-30V)) x 12A 1.5 kilowatts (kW)

[0065] For example, using an inverse compliance curve, the power consumption of the output stage is determined as follows:

[0066] (5V+2V) x 2A = 14 watts (W)

[0067] Six channels are used to achieve a total output of 12A, generating a power output of 14W x 6 = 84W. As mentioned, the physical size of the output stage scales up, for example, as power increases, and thus the size of the circuit required to generate that power output also increases. By requiring less power (84W vs. 1512W) to output the same amount of current (12A), the circuit of the test channel, which is controlled based on the inverse compliance curve, can be reduced in size. Additionally, because the circuit is smaller, a larger number of test channels can be placed in the same space, thereby increasing the density of the test channels.

[0068] In some implementations, when the VI test instrument is used as a Device Power Supply (DPS), allowing the output stage's upper power supply to ramp the voltage and current output power voltage (FV) ramps enables the full rated current during the DPS voltage ramp. In some implementations, the output stage voltage rails or rails can track the DUT voltage in real time. Implementations of test channels that include this feature actively measure the resistance of the power and return paths and automatically adjust the output stage voltage based on this information. For example, the output stage voltage can be adjusted to control the power output to maintain the power output within the range of a selected compliance curve.

[0069] Referring to FIG. 9, a process (80) for controlling a test channel includes, but is not limited to, the following operations. The process includes the step (81) of receiving a voltage as an input to a test system. For example, the voltage may be programmed into a test computer by a user, such as a test engineer. The voltage is a target forced voltage for the output of the test channel of interest. The process includes the step (82) of selecting a compliance curve based on the voltage. This selection may be performed by a user or by a processing unit controlling the test system, such as an ATE (10). The process includes the step (83) of generating a current output based on the voltage input and the compliance curve as previously described. The voltage and current are output to the test channel (84) as part of the test process. As previously described, in some implementations, the current may be programmed into the test computer by a user, such as a test engineer, and the voltage may not be known to be determined.

[0070] The exemplary systems and processes described herein may be used with any suitable test system. For example, the systems and processes may be used with high-voltage, low-current VI devices, where examples of high voltage are 100 V or higher and examples of low current are 200 milliamperes (mA) or lower. For example, the systems and processes may be used with high-voltage, low-current non-floating devices or high-voltage, high-current floating test devices.

[0071] All or part of the test systems and processes described herein and various modifications thereof may be configured or controlled at least partially by one or more computers using one or more computer programs implemented in type on one or more information carriers, such as on one or more non-transient machine-readable media. Computer programs may be written in any form of programming language, including compiled or interpreted languages, and may be distributed in any form, including standalone programs or modules, parts, subroutines, or other units suitable for use in a computer environment. Computer programs may be distributed to run on one computer or multiple computers at one site, or distributed to multiple sites and interconnected via a network.

[0072] Tasks related to configuring or controlling test systems and processes may be performed by one or more programmable processors running one or more computer programs to control all or part of the previously described well-formed tasks. All or part of the test systems and processes may be configured or controlled by dedicated logic circuits such as Field Programmable Gate Arrays (FPGAs) and / or Application-Specific-Integrated Circuits (ASICs).

[0073] Processors suitable for executing computer programs include, for example, general-purpose and dedicated microprocessors, and any one or more processors of any type of digital computer. Generally, a processor receives instructions and data from read-only storage areas or random access storage areas, or both. An element of a computer includes one or more processors for executing instructions and one or more storage area devices for storing instructions and data. Generally, a computer also includes one or more machine-readable storage media, such as mass storage devices for storing data like magnetic, magneto-optical disks, or optical disks, or is operably connected thereto to receive data, transmit data, or both. Non-transient machine-readable storage media suitable for implementing computer program instructions and data include, for example, semiconductor storage area devices such as EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), and flash storage area devices; magnetic disks such as embedded hard disks or removable disks; magneto-optical disks; and includes all forms of non-volatile storage areas, including CD-ROMs (Compact Disc Read Only Memory) and DVD-ROMs (Digital Versatile Disc Read Only Memory).

[0074] The elements of the different implementations described may be combined to form other implementations not previously specifically described. The elements may generally be excluded from the previously described system without adversely affecting their operation or the operation of the system. Additionally, various distinct elements may be combined into one or more individual elements to perform the functions described herein.

[0075] Other implementations not specifically described in this specification are also within the scope of the following claims.

Claims

Claim 1 A test system comprising: an output stage including a power amplifier circuit that applies voltage or current to a test channel; and one or more processing units for selecting a compliance curve among a first compliance curve and a second compliance curve for the output stage, wherein the compliance curve relates the output of the voltage to the output of the current for the output stage, and according to the first compliance curve, the voltage increases as the current increases, and according to the second compliance curve, the voltage increases as the current decreases; wherein the one or more processing units control the power amplifier circuit to follow the selected compliance curve, and the selected compliance curve is the first compliance curve or the second compliance curve. Claim 2 A test system according to claim 1, characterized in that the voltage is a direct current (DC) voltage and the current is a DC current. Claim 3 A test system according to claim 1, further comprising a compensation loop, wherein the compensation loop comprises: a voltage sensor for detecting the voltage on the test channel; a current sensor for detecting the current on the test channel; and one or more processing units for controlling the power amplifier circuit based on the voltage detected on the test channel and the current detected on the test channel. Claim 4 A test system according to claim 3, further comprising a current clamp that limits the current on the test channel when the current detected on the test channel exceeds a predefined maximum value. Claim 5 A test system according to claim 1, wherein the compliance curve is based on the magnitude of power that the output stage can consume. Claim 6 A test system according to claim 1, wherein the memory stores information for generating the first compliance curve and the second compliance curve or the second compliance curve; and the one or more processing devices are configured to select the compliance curve based on user or program input. Claim 7 A test system according to claim 1, characterized in that at least one of the first compliance curve or the second compliance curve includes a step function. Claim 8 A test system according to claim 6, wherein the first compliance curve includes a step function and the second compliance curve includes a step function. Claim 9 A test system according to claim 1, wherein the one or more processing devices are configured to implement a controller including a proportional-integral-derivative controller for controlling the power amplifier circuit. Claim 10 A test system according to claim 1, further comprising: a display device for displaying a function based on the compliance curve to a user; and an input device for programming the voltage according to the function. Claim 11 A test system characterized in that, in claim 10, the function is the compliance curve. Claim 12 A test system according to claim 10, characterized in that the function is a step function that falls within the boundary of the compliance curve. Claim 13 A test system according to claim 1, wherein controlling the power amplifier circuit to follow the selected compliance curve includes the step of setting the current; wherein the step of setting the current is based on the magnitude of power that the output stage can consume, the maximum voltage, and the voltage programmed into the test system. Claim 14 In claim 13, the step of setting the current is characterized in that the voltage programmed into the test system is adjusted to be less than or equal to the difference between the maximum voltage and the overhead voltage. Claim 15 A test system according to claim 1, wherein the output stage is connected to a reference voltage and a return conductor, the reference voltage is higher than the voltage of the return conductor, and the voltage of the return conductor is a predetermined value that is not zero. Claim 16 A test system according to claim 1, wherein controlling the power amplifier circuit to follow the first compliance curve includes the step of setting the current based on the voltage programmed into the test system; and wherein the first compliance curve enables a test channel density greater than the test channel density enabled by the second compliance curve. Claim 17 A test system characterized in that, in claim 16, the output stage has a physical size corresponding to the power consumption of the output stage. Claim 18 A test system according to claim 1, wherein the output stage is connected to a first reference voltage and a second reference voltage, and the first reference voltage is higher than the second reference voltage; the test system further includes a voltage sensor for detecting the voltage on the test channel; and the one or more processing devices are configured to control at least one of the first reference voltage or the second reference voltage based on the voltage on the test channel to control the power output for the test channel. Claim 19 A test system according to claim 1, wherein the output stage is connected to a first reference voltage and a second reference voltage, and the first reference voltage is higher than the second reference voltage; and at least one of the first reference voltage or the second reference voltage is programmable. Claim 20 A test system according to claim 1, further comprising a memory for storing a function that generates the first compliance curve or the second compliance curve. Claim 21 A test system according to claim 1, wherein the first compliance curve includes a curve in which the current increases as the voltage increases up to a certain point; and thereafter, the current is maintained constant over the increasing voltage range. Claim 22 A test system according to claim 1, characterized in that the voltage is an alternating current (AC) voltage and the current is an AC current. Claim 23 A test method characterized by comprising: receiving a value for a voltage as an input to a test system; selecting a compliance curve among a first compliance curve and a second compliance curve for the same output stage, wherein the selected compliance curve relates the output of the voltage to the output of the current for the output stage, wherein according to the first compliance curve, the voltage increases as the current increases, and according to the second compliance curve, the voltage increases as the current decreases, and the selected compliance curve is the first compliance curve or the second compliance curve and is based on the value for the input voltage; generating a current output based on the input of the voltage and the selected compliance curve; and applying the voltage and the current to the test channel. Claim 24 A test system comprising: an output stage including a power amplifier circuit that applies voltage or current to a test channel which is part of a connection to a device under test (DUT); a current clamp that limits the current on the test channel; and one or more processing units that select a compliance curve among a first compliance curve and a second compliance curve for the output stage, wherein the compliance curve relates the output of the voltage to the output of the current for the output stage, and according to the first compliance curve, the voltage increases as the current increases, and according to the second compliance curve, the voltage increases as the current decreases; wherein the one or more processing units control the power amplifier circuit to follow the selected compliance curve, and the selected compliance curve is the first compliance curve or the second compliance curve, and the one or more processing units are configured to dynamically control the current clamp based on the voltage across the DUT to control the curvature of the selected compliance curve. Claim 25 A test system according to claim 24, characterized in that power consumption through the output stage is based on the product of the difference between the voltage across the output stage and the voltage across the DUT and the current through the DUT. Claim 26 A test system according to claim 24, characterized in that dynamically controlling the current clamp includes the step of controlling the limit of the current on the test channel. Claim 27 A test system according to claim 24, wherein controlling the current clamp includes the step of programming the current clamp. Claim 28 A test system according to claim 24, wherein one or more processing devices are configured to control the power amplifier circuit to follow the selected compliance curve.

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